1. Field of the Invention
The invention relates generally to the field of slidably movable, track mounted panels and the like supported by counterbalance systems, and in particular, to a tip-lock shoe for window sashes and the like, which prevents such window sashes and the like from accidentally falling upon catastrophic failure of the counterbalance system.
2. Description of the Prior Art
Modern window assemblies are provided with means for enabling window sashes to be tilted into a room in order to facilitate installation, periodic cleaning and repair. Such window sashes are typically attached to shoes which are slidably mounted in vertically oriented tracks disposed on either side of the window frame. The shoes provide a point of interconnection between the window sash and the counterbalance system which enables the window sash to be easily raised and lowered, and which prevents the window sash from moving out of any opened or closed position in which it is placed. Such shoes are usually referred to as tip-lock shoes. Tip-lock shoes are provided with a braking mechanism by means of which the tip-lock shoe is locked into position into the track whenever the window sash is tilted out of a vertical orientation. The tip-lock shoe therefore provides a convenient means for controlling aligned movement of the window sash within the window frame, and at the same time, a reliable pivot point for periodic cleaning and maintenance. Tip-lock shoes of the kind described above are disclosed and described in the following U.S. Pat. Nos.: 3,055,063; 3,184,784; 3,197,819; 3,434,236; 3,434,237; 3,464,157; 3,482,354; 3,611,636; 3,789,549; 3,797,168; 3,844,066; 3,861,082; 4,028,849; 4,068,406; 4,079,549; 4,115,973; 4,364,199; 4,452,012; 4,590,708; 4,683,675; 4,683,676; and 4,718,194. The tip-lock shoes described in the foregoing patent references are of the widest possible variety in mechanical composition. Although each is characterized by the tip-lock feature described above, none discloses an independently operable trigger or mechanism for locking the shoe in position in the track automatically responsive to a catastrophic failure of the counterbalance system. Moreover, none of the tip-lock shoes disclosed in such references are inherently capable of automatically locking the shoe into a fixed position upon catastrophic failure of the counterbalance system.
The fail-safe tip-lock shoe disclosed herein is the first such tip-lock shoe capable of automatically preventing accidental movement of a window sash or the like upon catastrophic failure of a counterbalance system. Moreover, the fail-safe braking mechanism can be embodied without substantially increasing the dimensions of an otherwise typical tip-lock shoe, and without impairing the tilt-and-lock feature for which tip-lock shoes are named.